Transmission protocols, such as SONET (Synchronous Optical Networking) and SDH (Synchronous Digital Hierarchy), transmit data in structured frames. The SONET/SDH frame structure includes frameword bytes 10, 11 and payload bytes 14, as shown in FIG. 1. The frameword bytes contain N×A1 bytes (A1 typically has a value of F6H) and N×A2 bytes (A2 typically has a value of 28H), where N is an integer that depends on the data transmission rate (N=1, 3, 12, 48, etc.) and subscript “H” stands for hexadecimal (also referred to as “HEX”). Frameword bytes are used to delineate a frame and payload bytes carry the data transmitted in that frame.
Data frames are transmitted over an optical network in a serial data stream. A de-serializer device is required at the termination of the optical network in order to convert the serial data stream to parallel data. The conversion, however, can change the byte alignment (phase) of the frames. As a result, the frame and byte boundaries of the converted data are unknown. A data framer may be used at the recipient end of the optical network to restructure the frame and thereby correct any misalignment (i.e., phase errors).